Hello! I'm trying to have my first patterns in the downloads section (yep, some may recognize it being Honeywell's ones ! I'm trying some conversion) and the mod who picked them talked about transforming some from 1 into more channels.
Hey, cool! I'm on it! :DDD

But here's the thing, doesn't matter how carefully I select or paint the masks both on photoshop (CS5) and Gimp (2.8.22), they look fine until I save in .DDS (both using the latest .DDS plugins)
EDIT: I'm using DXT5 ARGB 8 for Photoshop and BC3/DTX5 for Gimp

Both images are below with Delphy's preview on the left. On the right the images BEFORE being saved in .DDS. Photoshop do the worst job for sure, but gimp still have issues at some parts. I tried coming back and editing the dds versions, but after saving the pixelization comes back and in the very same points, and worse than before! It's not really visible if you leave the pattern with a dark background, darker leaves and light color flowers but that almost makes the 3 channel a "meh" option since you would need to always be careful.

There is an alternative program you could use for exporting DDS, so you aren't focused on just nvidea's one. I have checked it out slightly, and since it's not an unknown thing that Directx 9 supported DDS types (DXT1, DTX3 and DXT5) are... crap. In fact, most gaming companies back then made their own DDS tools at one point due to the other ones being utter crap quality wise. It does however also support DXT10 and DXT11 (So directx 10 and directx 11) Which, we all know, give a way better result than the DXT9 ones. Unfortunately, for the sims 3 that won't be an option since it's built on Directx 9, thus, not being able to read the DXT10 and 11 data on textures or the DDS files. You could however try this tool out: